Knowledge of the most frequent words in a user's personal data, including email, is very useful because it can help predict user behavior. This knowledge can be useful, for example, in creating an advertising strategy for the user or in an application that automatically organizes the user's information.
Modern email systems have the capability of receiving voice mail messages and transcribing the voice mail messages into text messages that can be stored in a user's mailbox. Knowledge of the most frequently used words in a user's mailbox can also be used as an aid to machine-based recognition software to more accurately transcribe voice mail messages into text messages.